When reading those threads, Floyd, keep in mind that one needs to view the decision in terms of the entire system, not just as isolated attributes of any system. Removing the cantilever may exacerbate rim restriction in a small piano, or any piano, if one simply trades out the cantilever component, without accommodating rim conditions of the current soundboard setup. This includes proximity of the bridge root to the rim, orientation of the bridge relative to the panel grain, scaling of the wraps, thickness of the panel...and probably some others I've omitted.
When cantilevers are removed, its mostly on a new board which has been designed with a non-cantilevered bridge in mind. These redesigns will also often include a bass float to address the reduced proximity of the bridge-to-board contact in relative to the rim. As well the board may or may not be thinned aggressively back there, depending on the rebuilder.
Of all the small piano challenges to be considered in a design, I find adequate monochord tone one of the easiest to achieve...with the float and scaling figuring on the top of my list, its a sure win.
Bichords are more problematic, and must be approached carefully. The removal of the cantilever, if a bass float has been excluded, may well end up with a nasal bichord section. Even with the float, the bichords can end up nasal, so I pay attention here, especially as the bichords are much more important, in my opinion, from a pianist's point of view, than the very low bass. Basically, my take is, that the bass bridge in a 5ft grand is oriented almost perpendicular to the grain of the panel. This makes the bridge into an unintentional, humongous and unhelpful beam, right next to the rim. So in my small grand, non-cantilevered setup, the float must be included. I also design a linear length progression on the bass bridge, so I can make the bridge into a straight beam. Then, that straight beam only connects the panel at the ends, not in the middle at all, getting it off the crossgrain of the panel. Since the bridge is a straight beam, there is no tendency (or limited) to rotate under load. If the original curved root had been retained, with the root not contacting the panel mid-span, the same rotational tendency that the cantilever introduced would be re-introduced into the new non-cantilever, gaining nothing..
The byword is...look at the whole system when trying to suss these things out, rather than as a collection of individual isolated components.
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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Original Message:
Sent: 01-06-2018 11:36
From: Roger Gable
Subject: Bass bridge cantilever
Floyd,
Cantilever bridges are a way to maximize string length while optimizing soundboard impedance. Bass string frequencies (20-100 hertz) may not "match" the soundboard impedance at the revised point you propose. This may be due to the specific stiffness of the board directly under the current bridge cap. I suspect cantilevering would be found most often on small pianos where the soundboard is naturally stiffer. You may find the end results producing a weaker fundamental response. Generally, designers and manufacturers of these pianos have more resources than we do to test their products. I would keep the current design.
Roger
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Roger Gable
Gable Piano
Everett WA
425-252-5000
Original Message:
Sent: 01-04-2018 16:24
From: Floyd Gadd
Subject: Bass bridge cantilever
I am looking at a 1920 Harrington 5 foot something grand. The bass bridge has a rather large cantilever, and both the shelf and the cap are in poor condition. I have read on this list that the idea of cantilevering a bass bridge is counterproductive. If I replace this bridge, should I simply root it to the soundboard directly beneath the cap?
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Floyd Gadd
Regina SK
306-502-9103
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